1. Field of the Invention
The present invention relates to an antenna for communication, and, in particular, to a multi-band antenna which is applied to a terminal such as a mobile phone.
2. Description of the Related Art
With the recent rapid development of mobile communication and satellite communication technologies, there is an increasing importance of wireless communication in information society. Wireless communication technology, which originated from voice-oriented narrow-band communication, is rapidly developing into broadband communication for Internet, multimedia, etc.
Commercialization of new wireless services, such as 4th generation mobile communication based on IMT-2000 and high-speed mobile communication, is close at hand. Antenna technology is a major technology that forms the basis of wireless communication, and the importance of antenna technology increases daily since a mobile phone's antenna performance is a factor that determines communication quality.
As provision of various services in numerous fields, such as cellular mobile communication, Personal Communications Service (PCS), satellite mobile communication, etc. is possible as various communication services develop, intensive research is being conducted on wireless access schemes, and power/interference control, as well as terminal and network system technology for realization of miniaturization and reduction in weight of communication equipment for terminals and base stations.
An increasing popularization of mobile phones capable of providing the various services continues to bring new terminals with various functions and designs.
The recent trend in mobile phones is that consumers prefer, rather than bar type terminals, folder type or flip-up type terminals having a main body and a sub-body. The sub-body, also referred to as a folder, is mounted on the main body so that it can be opened and closed at a predetermined angle via a hinge module.
The folder type terminal has an advantage in that when its sub-body (including flip cover or folder) is coupled to the main body, the multiple key buttons formed on the main body are protected to prevent misoperation of the device. When open, the folder serves as a sound reflection plate during a call to concentrate the voice on a certain point. In addition, a wide Liquid Crystal Display (LCD) module can be individually mounted on the folder module of the folder type terminal, allowing the terminal to be miniaturized while providing a variety of functions.
Normally, a hinge module for opening and closing the sub-body on the main body at a predetermined angle is mounted in the folder type terminal. The hinge module serves not only to define a predetermined opening/closing angle of the sub-body, but also to store a predetermined elasticity when it is folded, so as to prevent the folder from being arbitrarily opened.
In addition to the demand for smaller, lighter and thinner terminals, there is a demand for terminals that provide a variety of functions. In order to meet such consumer demands, emphasis is placed laid on reducing the size or volume of the terminals if possible while maintaining or improving the functions.
In addition to the demand for smaller and lighter weight terminals that maximize the variety of functions, there is an increasing demand for convenience. To meet the demands, terminal makers concentrate their efforts on removing the various inconvenience aspects that may occur during use of the mobile phones.
Due to such problems, multi-band mobile phones, which support more than two frequency bands to enable both the old services and new services, are becoming increasingly more popular.
Therefore, antennas for the mobile phones are also developing into multi-band antennas supporting more than one frequency band. For example, generally, Code Division Multiple Access (CDMA) operates in a frequency band of 824 MHz˜894 MHz, while PCS operates in a frequency band of 1850 MHz˜1990 MHz. As one mobile phone can support both the CDMA band and the PCS band, dual-band antennas have been developed that can support both 824 MHz˜894 MHz and 1850 MHz˜1990 MHz frequency bands.
Recently, there is an increasing need for triple-band antennas supporting CDMA/PCS/GPS bands including a Global Positioning System (GPS) band of 1574 MHz˜1576 MHz. Accordingly, multi-band antennas are provided to extend the upper and/or lower bands of the existing single/dual-band antennas. Recently, in order to provide fine designs of mobile phones that are convenient to use, internal antennas rather than external antennas are popularly used.
For example, an internal antenna (‘Intenna’) chiefly used for a mobile phone can be classified into Planar Inverted F Antenna (PIFA) type, Loop type, and Monopole type.
FIGS. 1A and 1B are perspective views illustrating an internal antenna applied to the conventional mobile phone. Referring to FIG. 1A, the general internal antenna is mostly situated in an upper end of the mobile phone. Although the position of the internal antenna is subject to slight change according to the internal structure of the mobile phone, the internal antenna is formed on the upper end in most cases, to maximize antenna performance.
FIG. 1B provides an example of a PIFA/Loop type Intenna that includes an Intenna patch, a feeding port 101 connected to the Intenna patch and a ground port 102.
The PIFA Intenna should be designed to provide antenna characteristics best suited for a particular terminal. In this case, the antenna device is designed taking into account fixed design parameters and variable design parameters. Regarding the fixed design parameters, a length and width of a radiator, and a spaced distance between a ground surface and the radiator are roughly determined according to the predetermined shape and size of the terminal.
Therefore, the best antenna characteristics can be found by changing the variable design parameters during antenna characteristic matching. The variable design parameters can include a position of a feeding pin, a width of the feeding pin and a ground pin, a spaced distance between the feeding pin and the ground pin, a shape of a pattern formed on the radiator, etc.
Since the antenna applied to the conventional mobile phone is realized in a single pattern regardless of its frequency mode, i.e., regardless of whether its frequency mode is a single-band mode or a multi-band mode, each band individually suffers from a reduction not only in mute performance but also in antenna radiation characteristics. In order to solve the problems, antenna gain may be increased to improve the mute performance, which, however, causes an increase in Specific Absorption Rate (SAR) as a side effect.